.beta.-Lactam antibiotics are an important group of compounds in man's struggle against infectious diseases. The most important .beta.-lactams are the penicillins and cephalosporins which contain another ring system, either thiazine or thiazole, as an intricate part of the total molecule. In general, only bicyclic .beta.-lactams have sufficient antibacterial activity to be commercially useful. Many monocyclic .beta.-lactams have been reported in the literature primarily as degradation products of penicillins or cephalosporins or as synthetic precursors for pencillins and cephalosporins. However, significant biological activity has not been reported for these monocyclic .beta.-lactams. U.S. Pat. Nos. 3,943,123; 3,840,556 and 3,920,696, an article in J. Med. Chem. 18, 625 (1975) and German Pat. No. 2,437,385 are illustrative of this point. One exception to this general rule is a monocyclic .beta.-lactam prepared by fermentation and recently reported in J. Amer. Chem. Soc., 98, 3023 (1976).
We have now discovered a new monocyclic .beta.-lactam system which is prepared by a totally synthetic method and which possesses good antibacterial activity.